There are signs Asian carp may have breached barriers designed to keep the prolific fish out of the Great Lakes, which could spell ecological disaster for the vital source of fresh water, authorities said on Friday.

Concentrations of DNA discovered by Notre Dame University researchers may indicate the presence of bighead and silver carp upstream from two electrical barriers designed to bottle up the invasive fish.

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Environmentalists say that if the fish reach the Great Lakes, about 20 miles from the barriers, they would quickly destroy the lakes' $4.5 billion fishery by consuming other fish and their food sources. Only Lake Superior among the five lakes may be too cold for the carp, which can reproduce rapidly and reach 100 pounds (45 kg).

The Great Lakes are the world's largest body of surface fresh water and are relied on by 30 million people in the United States and Canada for drinking water and recreation.

"This is devastating news," Andy Buchsbaum of the National Wildlife Federation said of the discovery of carp DNA in the Cal-Sag channel 8 miles from Lake Michigan.

"We have to hope that there aren't enough population of fish to reproduce and create an epidemic of Asian carp in the lakes," he said.